It seems as if there is no answer in the "Service Department" world for my poor trucks problems... So I turn to you all!

My Ranger has two problems: one, when I shift into neutral after driving the engine keeps an idle at around 3k for around 7 seconds, then is notches it way back down to normal 1-1.5k. It idles normally after that until the next time I have to come to a stop. It seems related to the amount of throttle I am giving right before I have to stop. If I have been coasting (foot off gas pedal) in a gear before stopping and going into "N" then it does not rev up so high. But if I had to come to a quick stop or on a hill and only took my foot off the throttle seconds before I put it into neutral...then it revs up higher. If I press on the gas pedal during the time it is idling high...it then stays higher for the few seconds until it starts notching it's way back down. We replaced the IAC and it did not help the problem. They are telling me it is the PCM and that I should replace it. Should I not first try replacing the TPS?

Second problem...unrelated. I feel a slight hesitation, especially when a load is put on the engine, as going up an incline. I do feel the hesitation on flat land and going downhill too but not as much. The engine idles smoothly, do not feel any "misses" during idle. Spark plugs and wires all new...still problem exist. What should I look at next?

Thanks...Cathy T

 

What year is the truck, and does it have a 3.0L or a 4.0L engine?

 

98 Ranger XLT, 3.0L V6

 

Some of the '98 Rangers had computer calibration issues. You might want to talk to your dealer and find out if yours is one of them. Refer them to this Technical Service Bulletin:

 

Thanks! Could that cause the slight hesitation I've been feeling too?

 

Not sure about the hesitation. I'm not even sure about the computer calibration issue, but you ought to at least check.

Another common cause of idle problems is the Idle Air Control (IAC) valve, which along with the engine computer, is directly responsible for controlling idle.

 

Mr Rockledge,
She already replaced the IAC, but I wonder if there is a similar calibration change for a 3.8 in a '97 T-bird my wife drives. Irregularly, it will keep the rpms at 1200-1500 for a while after you release the accelerator. I removed & cleaned the IAC with some carb cleaner, and it seemed to be working better, but I think it may just be in my head..
So, question is, Is there a TSB for the '97 vintage 3.8 engines?
tom

 

Can the PCM just be reprogrammed or do I need to replace the entire piece? Ford suggested replacing, no mention of reprogramming.

 

I checked, but no TSB like that for the '97 3.8L. A few thoughts on your wife's T-Bird are that it could still be the IAC valve. From all that I have seen and heard, cleaning the IAC valve on "newer" 95+ vehicles seldom works.

You should also check the throttle cable/crusie control linkage, maybe spray some dry lube on all the moving areas on the TB and cables, make sure they are not sticking.

The throttle position sensor (TPS) also plays a role in maintaining proper idle upon deceleration: TPS Summary & Test

 

Should be able to just re-program it, but I don't know what the current protocol is for this issue.

Did the dealer confirm for you that your Ranger's PCM is one of those covered by the TSB?

 

reprogramming PCM may fix it the tsb sounds good reprogramming PCM is dealer thing or a well equipted shop, but you need to get the codes out of it may be a TP sensor code there, could not imagine a need to replace PCM(expensive) without doing much more testing, get the codes first.

 

Thanks...I appreciate everyones inputs. Rockledge, my dealership said nothing but that they called the "Ford Hotline" who then suggested replacing the PCM. I asked about the TPS and they said nothing about testing it, so I appreciate all the info you have already given me to continue my quest of finding someone to spend a little more time diagnosing/testing instead of replacing. The PCM would cost me $330 plus $196 labor. Here is all the dealership stated: " EEC TEST P1000. RUN OAISS SSMS 13835/05000 FOR RPM ON DECEL 1500-2000 RPM. CALL HOT LINE SEVERAL CASES FROM NORMAL TO PCM. T-BODY OR T-P SENSOR CONCERNS. PID MONITOR ROAD TEST IAC DROPING LOWER THAN EXPECTED. CHECK FOR VACCUM LEAKS OK. FOUND AFTER MARKET PCV VALVE. REPLACED PCV AND TOAD TEST IAC COMES UP CONCERNS STILL PRESENT. LEAD TECH RECOMENDS TO REPLACE PCM AND RECHECK."

So...common sense is telling me to ask about reprogramming the PCM and testing the TPS before going and replacing the PCM...!? If the TPS was "bad" would I be seeing/feeling or hearing anything while I am in a gear? Because all is normal (except for the slight hesitation) when I'm in gear.

 

I wish all mechanics could write complete sentences. The explanation mostly makes sense, but. He says the IAC is going "lower than expected". In my mind, I'd say that the IAC is 'closing' more than expected, as, somehow, there is extra air getting in and allowing the rpms to be higher than the ECM commanded, thus the ECM commands lower IAC air flow. He then reports vacuum test, replace non-Ford PCV and from there on makes a jump I don't get: replace PCM.(ECM)
AND: for pete's sake, the PCM is mounted so it can be removed (and replaced) in most cars, in less than 10 minutes. $196 labor SEEMS way too hi, but what do I know.
You got a test, with unclear diagnosis and the mech is suggesting to throw parts at it.

Get a new mech, they're cheaper.
tom

 

I like tom's thinking. He points out a few things that I agree with (1) can't rule out the IAC valve itself, (2) check for vacuum leaks everywhere, and (3) that seems like a lot of $$ to simply replace a PCM.

 

You guys Rock! Thanks.